AB0156 MECHANOTRANSDUCTION VIA MYOSIN II ISOFORMS IN DEVELOPMENT OF SKIN FIBROSIS WITHIN SYSTEMIC SCLEROSIS
Authors: B. Russo, M. Shutova, G. Romanescu, N. Brembilla, W. H. Boehncke
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Skin fibrosis, the hallmark of systemic sclerosis (SSc), is a complex inflammatory process leading to excessive extracellular matrix (ECM) deposition and increased stiffness in the dermis [1]. The mechanical properties of the extracellular environment can be sensed by the cells and transformed into intracellular signalling and gene expression regulation in the process of mechanotransduction. The upregulation of mechanotransduction has been linked to the progression of fibrosis in SSc, particularly through the Rho-ROCK-dependent myosin II pathway, which activates intracellular contractility [2]. Nonmuscle myosin II itself is expressed as three isoforms (NMIIA, NMIIB, NMIIC) with common and unique functions. However, the specific role of Rho activation and distinct NMII isoforms in SSc pathogenesis is unknown. <h3>Objectives</h3> To investigate the role of NMII isoform regulation in the development of skin fibrosis in SSc. <h3>Methods</h3> The expression of NMIIA and NMIIB, as well as their activation through phosphorylation of Myosin Light Chain (MLC) were evaluated by immunofluorescence in primary fibroblasts from four SSc and four healthy donor (HD), which were stimulated with rhTGFβ. The NMII contractility was inhibited with Y-27632, a small molecule inhibitor of ROCK that phosphorylate MLC, or blebbistatin, a small molecule that inhibit NMII. The production of IL-6 and type-I collagen by fibroblasts was assessed by ELISA. <h3>Results</h3> We have observed a re-distribution of NMII isoforms within the intracellular contractile system and increased MLC phosphorylation in cultured SSc fibroblasts compared to HD. A similar phenotype was observed in HD fibroblasts primed with TGFβ. Treatment of TGFβ-primed HD fibroblasts with Y-27632 or blebbistatin substantially reduced IL-6 and collagen I production. <h3>Conclusion</h3> Our data point to an altered actomyosin cytoskeleton dynamics and force distribution in SSc fibroblasts and indicate that NMII isoforms are required for the TGFβ-dependent secretion of inflammatory cytokines and collagen deposition by fibroblasts. <h3>References</h3> [1]Gabrielli A, Avvedimento EV, Krieg T. Scleroderma. N Engl J Med.2009;360(19):1989-2003. [2]Demiryürek S, Baysalman E, Mammadov A, Demiryürek AT. Contribution of the Rho- kinase to Systemic Sclerosis and Behçet's Disease. Curr Pharm Des. 2018;24(29):3402-9. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Barbara Russo: None declared, Maria Shutova: None declared, George Romanescu: None declared, Nicolò Brembilla: None declared, Wolf-Henning Boehncke Speakers bureau: WH Boehncke has received honoraria as an advisor from the following companies: AbbVie, Almirall, BMS, Celgene, Leo, Lilly, Novartis and UCB. WHB has received honoraria as a speaker on the occasion of sponsored symposia from AbbVie, Almirall, Celgene, Leo and Novartis., Grant/research support from: WHB has received a research grant from Pfizer. AGA Kolios has served as an investigator, speaker and/or advisor for AbbVie, Abbott, Amgen, Celgene, Janssen, Eli Lilly, Leo, MSD, Novartis and Pfizer.